fix(installer): generate state.json from lib/state-schema.nix

Closes the last source-of-truth split after the state-defaults
centralization batches. The installer's heredoc was the only remaining
place that hardcoded the state.json literal — adding a default to the
schema previously required a parallel edit here, and silent drift was
exactly the bug class we kept fixing.

Before:

  cat > /mnt/etc/nixos/state.json <<JSON_EOF
  {
    "theme": "nord",
    "timezone": "${_state_tz}",
    "dns": "DHCP",
    ...
  }
  JSON_EOF

After:

  nix eval --impure --raw --expr "
    let
      flake = builtins.getFlake \"$NOMARCHY_REPO\";
      lib = flake.inputs.nixpkgs.lib;
      schema = import \"$NOMARCHY_REPO/lib/state-schema.nix\"
                 { inherit lib; };
      state = schema.system // { timezone = \"$_state_tz\"; };
    in builtins.toJSON state
  " | nrun jq '.' > /mnt/etc/nixos/state.json

Uses the flake's own pinned `inputs.nixpkgs` (matching what the rest of
Nomarchy resolves against), so the schema evaluates with the same `lib`
the consumer modules see. `nrun jq` pretty-prints for human inspection.

Behavioural notes:
- Output is identical to the old heredoc modulo alphabetical key
  ordering — `builtins.toJSON` sorts keys, the heredoc was in
  declaration order. Toggle scripts read/write via `jq` so it's
  invisible to them.
- Dry-run path unchanged. `execute_dry_run` already bind-mounts a fake
  /mnt for the generator; the generator's absolute paths still resolve.
- New schema fields show up automatically on the next install; no
  parallel edit needed.
- `bash -n` + `shellcheck --severity=error` clean.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

installer/install.sh

@@ -1799,30 +1799,29 @@ EOF
 }
 EOF
 
-    # state.json — consumed by core/system/state.nix at every nixos-rebuild and
-    # mutated by toggle scripts (nomarchy-tz-select, nomarchy-setup-fido2,
+    # state.json — consumed by core/system/state.nix at every nixos-rebuild
+    # and mutated by toggle scripts (nomarchy-tz-select, nomarchy-setup-fido2,
     # nomarchy-toggle-hybrid-gpu, nomarchy-wifi-powersave, ...). Those scripts
-    # `jq` the file in place and fail hard if it doesn't exist or isn't valid
-    # JSON, so a fresh install MUST ship one. Shape must match lib/state-schema.nix.
-    # Quoted heredoc — no shell expansion except the explicit $TIMEZONE below.
+    # `jq` the file in place and fail hard if it doesn't exist or isn't
+    # valid JSON, so a fresh install MUST ship one.
+    #
+    # Source of truth: lib/state-schema.nix. We eval its `system` block and
+    # overlay the installer-chosen timezone, so this generator no longer
+    # drifts from the schema or the *.nix consumers — the previous heredoc
+    # was the last source-of-truth split after the state centralization.
+    # Adding a new default in the schema now reaches the installer without
+    # any further plumbing.
     local _state_tz="${TIMEZONE:-UTC}"
-    cat > /mnt/etc/nixos/state.json <<JSON_EOF
-{
-  "theme": "nord",
-  "timezone": "${_state_tz}",
-  "dns": "DHCP",
-  "customDns": [],
-  "wifi": {
-    "powersave": true
-  },
-  "features": {
-    "fingerprint": false,
-    "fido2": false,
-    "hybridGPU": false,
-    "makima": false
-  }
-}
-JSON_EOF
+    nix --extra-experimental-features 'nix-command flakes' eval \
+        --impure --raw \
+        --expr "
+          let
+            flake = builtins.getFlake \"$NOMARCHY_REPO\";
+            lib = flake.inputs.nixpkgs.lib;
+            schema = import \"$NOMARCHY_REPO/lib/state-schema.nix\" { inherit lib; };
+            state = schema.system // { timezone = \"$_state_tz\"; };
+          in builtins.toJSON state
+        " | nrun jq '.' > /mnt/etc/nixos/state.json
 }
 
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